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They would be too bright, and too expensive. Those 5mm LEDs (outdated crap) have LED dies of a less than 1/20th of a mm^2 inside.

High-end power LEDs that put out the equivalent of a 100W incan bulb are 2-4mm^2.

A disk the size of a traffic light would be able to draw 10000s of Amps, and be bright enough to illuminate a stadium (if you could drain the waste-heat away). Driving it with lower currents would be a collosal waste of dies.

So the wavers are cut into conveniently sized pices that have reasonable power draw and thermal conductivity and then later are put together according to the requirements.

There isn't that much to gain from economy of scale, as those types of cells are already produced in 100s of millions per year. So we are realistically looking at something like halfing the price at most, not cutting it down by an order of magnitude or something.

Oh, yeah, you COULD do it.If you overengineered the ships (making them 5 times more expensive) AND had complete checks agter every 1000 operation hours of everything (which is basically every round-trip for a container ship).

Yes, there are speed limits quite commonly, but if you discount Stadtautobahn stuff and the Ruhrpott, 2/3rds of it are unlimited. Case in point: You can drive Stuttgart/Berlin and have all but 50km or so of the distance unlimited.

In theory. In practice, helium will interact with, for example, iron alloys (steel), ending up with de-electonized protons migrating through the bulk metal, and at the other end snatching up some of the fermi-gas and going their merry way.

The same way, in vacuum systems, getting rid out of the stupid hydrogen magically appearing out of nice stainless steel enclosures that have been ultrasonic cleaned and baked under vacuum is a real problem. I have seen suggestions of burning the whole chambers under vacuum at 650C to get the protons out, and even that isn't really the end of things.